﻿class GradeEvaluation

{

    static void Main()

    {

        int score = int.Parse(Console.ReadLine());

        if (score >= 90)

        {

            Console.WriteLine("A");

        }

        else if (score >= 60)

        {

            Console.WriteLine("B");

        }

        else

        {

            Console.WriteLine("C");

        }

    }

}